(a) Field of the Invention
This invention relates to photosensitive materials for use in electrophotography which comprise a conductive support coated with a photoconductive layer and a protective layer wherein said protective layer formed on said photoconductive layer comprises specifically selected components which improve the light-decay property, mechanical strength and image formability of said photosensitive materials.
(B) Description of the Prior Art
Photosensitive materials for use in electrophotography have benerally been provided by forming a photocontive layer consisting of an inorganic semi-conductor or an organic semi-conductor on a conductive support. To form an electrostatic latent image on such photosensitive materials, the so-called Carlson's process has been employed. This process comprises charging of the photoconductive layer side of the photosensitive material and image-like exposure. However, photosensitive materials of this type lack mechanical strength in the photoconductive layer and break easily when used repeatedly. To avoid this defect, there have hitherto been proposed a variety of photosensitive materials aimed at improving durability by providing a transparent protective film of resin formed on the photoconductive layer. Such photosensitive materials are disclosed in Japanese Patent Publication No. 23910/1967, Japanese Patent Publication No. 19748/1967, Japanese Patent Publication No. 24748/1968, Japanese Patent Publication No. 2965/1974, Japanese Patent Publication No. 15446/1963, Japanese Patent Publication No. 3713/1971, Laid-open Application No. 22036/1973 and U.S. Pat. No. 3,140,174. These proposed photosensitive materials are defective in that the provision of a protective layer has caused a deterioration of the light-decay property (sensitivity) inherent in the photoconductive layer, and a tendency to give rise to blurred images. Moreover, their mechanical strength is unsatisfactory. These deficiencies have been considered attributable to the insufficiency of the insulating property or the physical properties of the resin employed for the protective layer.
The present inventors have found that, by forming said protective layer utilizing specifically selected resins, or selected resins together with a silane-coupling agent, not only can the mechanical strength of the protective layer be improved, but also the adhesive property thereof to the photoconductive layer can be enhanced. Moreover, in neither case is there an insulating property of the protective layer, and in both cases the aforesaid defects of the conventional photosensitive materials are substantially eliminated.